Percussive tool



Sept. 17, 1940. w. A. SMITH, `sR '35,214,809`

. APERcUssIvE moor.

INVENTOR HIS ATTORNEY w. A. SMITH. 's

PERCUSS IVE TOOL Sept. 17, 1940.

Filed June 29, 1959 s sheets-sheet 3 HIS ATTORNEY.

Patented Sept. 17, 1940 lUNITED STATES PATENT OFFICE PERCUSSIVE TOOLApplication June 29, 1939, Serial No. 281,814

GCIaims.

This invention relates to percussive tools, and more particularly to aninternal combustion engine operated percussive tool of the type in whichthe working implement is capable of free reciprocatory movement withrespect to the element actuating it.

One object of the invention is to construct a rugged, compact andpowerful percussive tool that may be conveniently manipulated and guidedwith respect to the work and which will be capable of fulfilling all therequirements of a tool of this character in the various positions whichit may occupy in practice.

Other objects will be in part obvious and in part pointed outhereinafter.

In the drawings accompanying 'this specification and in which similarreference numerals refer to similar parts,

Figure 1 is a side elevation of lthe percussive tool constructed inaccordance with the practice of the invention.

Figure 2 is an elevation, partly in section, of the percussive tool,

Figure 3 is a transverse view,in section, taken through Figure 1 on theline 3 3 showing more particularly the interior of the percussiveelement,

Figure 4 is a transverse view, in section, taken through Figure 3 on theline 4 4,

Figure 5 is a view similar to Figure 3 taken on the line 5 5 in Figure 1and showing the interior of one of the power cylinders,

Figure 6 is a transverse fragmentary view, in section, taken throughFigure 5 on the line 6 6, and

Figure '7 is a view takeny through Figure 6 on the line 1 1.

Referring more particularly to the drawings, 2U designates, in general,a percussive tool, and 2i a working implement which the percussive toolyis intended to actuate.

In the form of the invention illustrated the percussive tool comprises acrank casing 22 supporting upon its rearward end a fuel tank 23 and atits forward end a pair of depending engine cylinders 24 and 25 and apercussive cylinder 26 arranged between the engine cylinders and axiallyof the percussive tool 20.

In accordance with the practice of the invention, the fuel tank, whichmay be rigidly secured to the crank casing 22 in any suitable manner,serves as a support for a handle 21 whereby the percussive tool may beguided. The fuel tank is accordingly provided with an internal rib 28which extends entirely therethrough and has a bore 23 to accommodate abolt 30 upon the ends of which are disposed grip members 3i.

At the upper end of the fueltank is a lling opening 32 normally sealedby a plug 33 and between the fuel tank and the crank casing 22 is a. pador gasket 34 of nonconducting material, such -as asbestos, to preventthe transmission of heat from the power element to the fuel tank.Bushings 35, also of asbestos, encircle the rearward ends of thecylinders 24 and 25 and seat in recesses 36 in the crank casing tominimize the flow of heat from the engine cylinders to the crank casing.

The interior of the crank casing 22 is divided into a plurality of crankchambers, three in the present instance designated 31, 38 vand 39, bywalls 40 arranged at spaced points within the crank casing. 'I'he walls40, together with the outer walls 4| of the crank casing, serve assupports for a crank shaft 42 which extends entirely through the crankcasing and carries on one exposed end lugs 43 for interlockingengagelment with clutch members 44 of a crank 45 whereby the crank shaftmay be rotated for start 25 ing the engine element of the tool.

The crank shaft has three crank pins 46, 41 and 48 each carrying aconnecting rod 49 of which two are connected to pistons 50 and 5I in thecylinders 24 and 25 and the remaining rod is connected to a plunger 52reciprocable in -a piston chamber 53 in the percussive cylinder 26. Thepower element of the tool operates on thetwo .cycle principle and eachpiston 50 and 5I is provided on its outer end or head with a baille 54to cause the incoming fuel charge to swerve downwardly into the lowerportions of the cylinders 24 and 25 and thereby avoid undue loss of un-`burned fuel through the exhaust ports 55 in the engine cylinders.

The fuel charge is ignited in the cylinders 24 and by sparking plugs 56suitably attached to the lower portions of the cylinders, and thesparking periods are controlled by a-timer 5I attached to an end of thecrank shaft 42. 'I'he timer 51 may be connected, in a well known manner,to a coil 58 attached to the side of the percussive tool and having acable 59 which may lead to a source of electrical supply, as for examplea battery (not shown).

As a preferred arrangement each engine cylinder is provided With anindividual fuel metering device arranged entirely within the casing ofthe percussive tool. These devices, of which only one is shown anddesignated 60, are arranged in the upper portion of the crank casing 22directly between the i'uel tank 23 and the adjacent crank chambers 31and 38 wherewith they communicate through passages 6| in the crankcasing.

Each metering device comprises a cylindrical member 62 which is disposedin al recess 63` in the crank casing and having a flange 64 at its upperend which is clamped between the gasket 34 and a shoulder 65 in therecess for holding the metering device xedly in position. In the centralportion of the member 62 is a hub 66 which is joined to the body of themember 62 by ribs 61 cooperating with the body portion of the member andthe hub to denne passages 6 8 through which the air constituent of .thefuel charge passes to the passage 6| and thus to the associated crankchamber. this purpose is conveyed to the passages 68 by channels 69extending through columns 10 within the fuel tank 23, and in therearward ends of the channels 69 are screen plugs 1| to prevent theentrance of abrasive matter into the channels 69.

'I'he air flow from the channel- 69 to the passage 6| is controlled by apoppet valve 12 which seats against the lower end surface 13 of thecylindrical member 62 and has an upwardly extending stem 14 slidable inthe bore 15 in the hub 66. In the upper end of the stem 14 is an annulargroove 16 to-receive a split collar 11 that seats into a depression 18of a sleeve 19 disposed about the stem 14, and on the periphery of thesleeve 19 is a ange 80 that serves as a seat for a spring 8| seated uponthe ribs 61 to normally press the valve 12 against the surface 13. Asuitable space 62 exists between the upper end of the hub 66 and thesleeve 19 to permit of a limited degree of endwise movement of the valvefor opening communication between the passages 68 and 6|. e

An additional function of the valve 12 is to controlcommunicationbetween the passage 6| and the interior ofthe fuel tank 23. Thecylindrical member 62 is accordingly provided with a plurality ofchannels 83 which extend from one end to the other of the cylindricalmember and have their outlet openings lying within the compass of thevalve 12 so that when the'valve is seated against the surface 13 theoutlet ends of the channels 83 will be fully sealed thereby.

In order to prevent clogging of he channels 83 by such particles offoreign; atter as may be entrained in the fuel, said channels arepreferably of considerably larger cross sectional area than the flowarea necessary for thefuel requirements of the power element of thetool, and filler pins 84 are disposed in the channels 83 to cooperatewith the walls thereof for dening restricted annular passages 85 throughwhich fuel may ow to the passage 6|. 'Ihe pins 84 are suspended in thechannels 83, having heads 86 that rest upon shoulders 81 at the upperends of the channels 83.

As a preferred arrangement the fuel is introduced into intermediateportions of the channels 83 by passages 88 extending through the member62 and the gasket 34 and opening into an annular supply chamber 89 onthe lower end of the fuel tank 23. The supply chamber 89 is in opencommunication with the interior of the fuel tank through passages 90.Between the supply chamber 89 and the passages 88 is a screen 9| toprevent foreign matter from entering the channels 83 and the associatedcrank chamber where the fuel charge is thoroughly mixed and from whenceit flows to the engine cylinders The air utilized for` through passages92 leading from the crank chambers to points in the cylindersapproximately in the same transverse plane as the exhaust ports 55.

- Although the percussive tool is provided, at various points, withinsulating members adapted to prevent the transmission of heat from theengine cylinders to adjacent portions of the structure it has been foundto be advantageous to provide means for causing the quick dissipation ofthe heat of combustion. To this end the percussive tool is provided witha blower or fan 93 for directing jets of air against the sides of thecylinders 24 and 25. The fan sa is driven by the crank shaft 42 and ismounted upon a shaft 94 carrying a pinion 95 that meshes with a gear 96keyed to a web 91 of the crank shaft.

'I'he fan is arranged in a chamber 98 in the side of the crank casingand a cover 99 for the chamber 98 supports an anti-friction bearing foran .end of the shaft 94. A similar bearing |0| is disposed in the crankcasing adjacent the pinion 95 to support the opposite end of the shaft94.

' In order to subject the fuel in the tank 23 to the cooling effect ofthe air impelled by the fan 93 and thus further reduce the chances ofvaporization of fuel in the tank, the inlet 'passage |02 for the fan isformed along the side of the fuel tank and is of considerable width sothat it extends along the major portion of such side. Owing to thisarrangement the inner wall |03 of the passage, and which wall forms#bounding surface for the fuel tank, will be kep at a low temperatureand thereby exert a coo ing effect upon the fuel.

The air discharged by the fan 93 passes into the chamber 98, th cevthrough a discharge port |04 in the cra casing and a nozzle v|05 havingtwo diverging branches |06 which are positioned so as to direct the airagainst the sides of the engine cylinders 24 and 25.

In addition to the cylinder 26 and the plunger 52 the percussive elementcomprises a hammer piston |01 reciprocable in the piston chamber |08containing the plunger 52 for delivering blows to the working implement2|, the shank of which extends into the front end of the piston chamberand carries a collar |09 for engagement with a steel retainer |||lcarried by a front head attached vto the cylinder 26 for guiding theworking implement. The hammer piston |01 is hollow having a cavity ||2to receive a reduced extension |I3 of the plunger wherewith the hammerpiston is in slidable and non-interlocking engagement.

The peripheral surface of the cavity ||2 serves as a guide for theextension I3 and the rearward end portion ||4 of the plunger is enlargedand in slidable engagement with the wall of the piston chamber. 'Iheplunger y52 is thus guided by the walls of the piston chamber and of thecavity ||2. By reason of this construction an annular chamber I5 willexist around the plunger 52 between the enlargement ||4 thereof and' therearward end surface- ||6 of the hammer piston.

The portion of the cavity |2 forwardly of the plunger 52 constitutes apressure chamber ||1 in which air is alternately compressed to transmitthe force of the plunger to the hammer piston on the power stroke of theplunger and expanded to a sub-atmospheric value on the return stroke 0Ithe plunger to cause the hammer piston |01 to be retracted to stroke.

In order to avoid the necessity'of maintaining a perfect seal betweenthe peripheral surface of the plunger 62 and the cooperating surface ofthe hammer piston for the sake-of preventing a diminution of the airentrapped in the pressure chamber I I1 it is contemplated to effect anintermitten admisssion of atmospheric air into the pressure chamber ||1to compensate for such air as may be forced from the cavity ||2 duringthe power stroke of the plunger of the hammer piston and during whichtime the air in the pressurel chamber ||1 will, of course, be materiallycompressed.

In the form of the invention illustrated, the air utilized for thispurpose is derived from the crank chamber 39 which the air entersthrough a passage ||8 in a rib ||9 extending through the fuel tank andhaving a strainer plug |20 at its outer end to filter the air.

The crank chamber 33 is in direct communication with the interior of theplunger 52, and in the enlarged portion |I4 of said plunger are radialports |2| which, in the extended position of the plunger, communicatewith an annular groove |22 in the wall of the piston chamber to permitthe passage of air from the cranlv: chamber into the annular chamber|I5.

Communication is aiforded between the annular chamber ||5 and thepressure chamber ||1 through channels in the periphery of the plungerand in the adjacent contacting surface of the hammer piston. 'I'hechannels in the plunger are in the form of longitudinally extendinggrooves |23 of such length that their rearward ends will be exposed bythe skirt of the hammer piston during the rearward stroke of the plungerand during which time the hammer piston will assume its most forwardlyposition with respect to the plunger. The grooves |23 preferably extendto points near the front or lower end of the plunger and are in constantcommunication with an annular groove |24 near the rearward end of thecavity ||2, and from the groove |24 extend grooves |25 forwardly alongthe wall of the cavity ||2 to a second annular groove I3 adjacent thepressure chamber I1.

Thus, in practice, when the plunger 52 starts forwardly on the workingstroke its initial movement will take place relatively to the hammerpiston and will cause the rearward ends of the grooves |23 to be coveredby the adjacent portion of the skirt of the hammer piston. Air will thenbe entrapped in the pressure chamber ||1 and be compressed, since itserves as the medium through which the force of the plunger 52 istransmitted to the hammer piston. and when the plunger reaches the endof its working stroke the hammer piston will be projected forwardlyagainst the working implement 2| to deliver its blow.

'Ihe forward movement of the hammer piston, relatively to the plunger52, will cause the rearward ends of the grooves |23 to be uncovered bythe hammer piston and air will then again be admitted into the pressurechamber ||1 through the grooves |23, |24 and |25. 'I'his admission ofmake-up air into the pressure chamber ||1 takes place during theinterval in which the ports |2| are in registry with the groove |22.

Upon reversal of the plunger the ports |2| are drawn out of registrywiththe groove |22 and the ensuing rearward movement of the plunger willcreate a sub-atmospheric pressure in the the starting position of thepower chambers I5 and I1 and cause the hammer piston to follow theplunger rearwardly.

The front end of the piston chamber, below the hammer piston 01, isnormally maintained in communication with the atmosphere so thatatmospheric pressure will be constantly present forwardly of the hammerpiston to impel it rearwardly in accordance with the rearward movementof the plunger 52. The air serving this function is, in the presentinstance, conveyed from the crank chamber 39 by a passage |26 in thecrank casing 22 and the cylinder 26 and opening into the front end ofthe piston chamber |08.

Interposed in the passage |26 is a valve |21 of the rotary plug typehaving a lever |28 whereby it may be manipulated, and in the valve |21is a passage |29 to normally afford communication between the associatedportions of the passage |26. 'I'he valve I 21 also has a port |30 which,when the valve is in position in which the passage |29 is out ofregistry with the passage |26, communicates with a portion of thepassage I 26 leading from the crank chamber 39 to the valve. In thisposition of the valve the passage |29 opens into an annularv groove |3|Within the piston chamber and said groove |3| is so located that whenthe hammer piston |01 reaches the working implement 2| ports |32 in thewall of the hammer piston will be in communication with the groove |3I.

Normally, the valve |21 occupies a position to prevent communicationbetween the passage |26 and the groove |3| and is only positioned toadmit air into the groove |3| and, therefore, into the pressure chamber||1 whenever it is intended to avoid the delivery of blows against theworking implement, as for example when shifting the percussive tool fromone drilling site to another while the engine element is in operation.In such case the valve |21 is rotated to a position in which the port|30 is in communication with the uppermost portion of the passage |26.Air will then flow through these passages and through the groove |3I andthe ports |32 into the front end of the cavity ||2 to maintainatmospheric pressure therein. The hammer piston |01 will then remainat'rest in the forward end of the piston chamber |06 and will beundisturbed by the movement of the plunger, since then the pressures inthe forward end of the piston chamber and within the cavity I I2 will bethe same.

Preferably, a port |33 is provided between the portion of the passage I26 lying forwardly or below the valve |21 and the adjacent portion ofthe piston chamber |08 so that when the working implement is removedfrom the path of the hammer piston, and in consequence of which thehammer piston |01 will rest upon the forward Wall of the piston chamber|08, the ports |32 will register with the port |33 to maintain thechamber ||1 in communication with the atmosphere and thereby avoid atendency, on the part of the hammer piston, to reciprocate while thepercussive tool is running idle. l

In order to assure a plentiful supply of lubricant to the bearings ofthe crank shaft 42 an oil chamber |34 is formed in the upper surface ofthe crank casing 22 and suitable oil passages |35 lead from the oilchamber to the bearings of the crank shaft. 'I'he oil passages |35 allextend in of oil in the chamber |34 and said opening |36 is sealed by aplug |31.

I claim:

1. A percussive tool, comprising a casing having a piston chamber, ahammer piston in the piston chamber having a pressure chamber, and aplunger slidable in the' piston chamber and in the pressure chamber foractuating the hammer piston and cooperating with the hammer piston tocreate a sub-atmospheric pressure in the pressure chamber to cause thehammer piston to follow the plunger in one direction.

2. A percussive tool, comprising a casing having a piston chamber, ahammer piston in the piston chamber having a pressure chamber, a plungerslidable in the piston chamber and in the pressure chamber for actuatingthe hammer piston and cooperating with the hammer piston to create asub-atmospheric pressure in the pressure chamber and thereby cause thehammer piston to follow the plunger in one direction, and means on theplunger and the hammer piston cooperating with each other tointermittently admit atmospheric air into the pressure chamber.

3. A percussive tool, comprising a casing having a piston chamber, ahammer piston in the piston chamber having a pressure chamber, a plungerslidable in the piston chamber and in the pressure chamber for actuatingthe hammer piston and cooperating with the hammer piston to create asub-atmospheric pressure in the pressure chamber and thereby cause thehammer piston to follow the plunger in one direction, passages in theplunger to convey atmospheric air into the pressure chamber, and meanson the'hammer piston to control the passages.

4. A percussive tool, comprising a casing having a piston chamber, ahammer piston in the piston chamber having a pressure chamber, a

plunger slidable in the piston chamber and in the pressure chamber foractuating the hammer piston and cooperating with the hammer piston tocreate a sub-atmospheric pressure in the pressure chamber and therebycause the hammer piston to follow the plunger in one direction, passagesin the cooperating surfaces of the plunger and the hammer piston toconvey atmospheric air into the pressure chamber, and means on thehammer piston cooperating with the plunger to control the passages.

5. A percussive tool, comprising a casing havingA a piston chamber, ahammer piston in the piston chamber having a pressure chamber, a plungerslidable in the piston chamber and the pressure chamber for actuatingthe hammer piston and cooperating with the hammer piston to create asub-atmospheric pressure in the pressure chamber to cause the hammerpiston to follow the plunger during alternate strokes of the plunger,vand manually operable means for selectively introducing atmospheric airinto the pressure chamber.

6. A percussive tool, comprising a casing having a piston chamber, ahammer piston in the piston chamber having a pressure chamber, a plungerslidable in the piston chamber and the pressure chamber and cooperatingwith the hammer piston to create a sub-atmospheric pressure in thepressure chamber to cause the hammer piston to follow the plunger duringalternate strokes of the plunger, a passage in the casing to conveyatmospheric air to the front end of the piston chamber, a passage in thehammer piston communicating with the pressure chamber, and a manuallyoperable valve to selectively control communication between thepassages.

WILLIAM A. SMITH, SR.

